1. Technical Field of the Invention
The present invention relates to mobile telecommunication networks supporting packet flows.
2. Description of Related Art
Currently there are different kinds of mobile telecommunication networks (or briefly referred to as “wireless network”) that offer pack packet-switched access.
One example of such a wireless network is the 3G mobile network according to 3GPP specifications. Such a network is composed by a number of different subnetworks: a Radio Access Network (RAN), based on different radio access technologies, a Packet-Switched (PS) Core Network (CN), and a Service Network implementing services and service enablers. Also included in such a system are mobile terminals (wireless telephones and data communication devices, also called user equipment—UE). FIG. 1 shows the overall network architecture of such a network.
A first example of such a RAN is Wideband Code-Division Multiple Access (WCDMA) RAN. WCDMA is a third generation mobile communication system that uses WCDMA technology. WCDMA provides for high-speed data and voice communication services. Installing or upgrading to WCDMA technology allows mobile service providers to offer their customers wireless broadband (high-speed Internet) services and to operate their systems more efficiently (more customers per cell site radio tower). The WCDMA RAN is composed of radio Base Stations (also called Node B), Radio Network Control (RNC) nodes and an interconnection system between these nodes (switches and data routers). A second example of a Radio Access Network that offers packet-switched access is the GSM RAN, also called General Packet Radio Service (GPRS), which is a packet data communication system that uses the Global System for Mobile (GSM) radio system packet radio transmission. The GSM RAN modifies the GSM channel allocation and time slot control processes to allow for the dynamic assignment of time slots to individual users. The nodes in a GSM RAN are the Base Transceiver Station (BTS, also called base station) and the Base Station Controller (BSC).
The Packet-Switched Core Network, also referred to as the GPRS CN, includes the following nodes:                Gateway GPRS Support Node (GGSN), which is a packet switching system that is used to connect a GSM mobile communication network (GPRS Support Nodes) to other packet networks such as the Internet; and        Serving GPRS Support Node (SGSN), which is a switching node in the wireless network that coordinates the operation of packet radios that are operating within its service coverage range. The SGSN operates in a similar process of a MSC and a VLR, except the SGSN performs packet switching instead of circuit switching. The SGSN registers and maintains a list of active packet data radios in its network and coordinates the packet transfer between the mobile radios.        
In a wireless network that offers packet-switched access, the operator provides not only the access, but may also provide services on top of this access. Examples of these services are premium video clips and multimedia services. The mechanisms for offering such services, as well as subscriber related functions for controlling access to the basic PS bearer services, are included in the Service Network. The Service Network may include many nodes, for instance the HLR (Home Location Register), application servers, proxy servers, policy decision functions, flow inspection functions, Border Gateways (BGW) for interconnecting to other networks and more.
In the cases where the operator provides and charges for an end-user service rather than the basic PS access, it is important for the operator to be able to control the quality of the service delivery.
The quality of the service delivery is highly dependent on the Bearer service. Bearer services are services that are used to transfer user data and control signals between two pieces of equipment. Bearer services can range from the transfer of low speed messages (300 bits per second) to very high-speed data signals (10+ Gigabits per second). Bearer services are typically categorized by their information transfer characteristics, methods of accessing the service, inter-working requirements (to other networks) and other general attributes. Information transfer characteristics include data transfer rate, delay requirements, direction(s) of data flow, type of data transfer (circuit or packet) and other physical characteristics. The access methods determine what parts of the system control may be affected by the bearer service. Some bearer services must cross different types of networks (e.g. wireless and wired) and the data and control information may need to be adjusted depending on the type of network.
The main service offered by a 3G mobile Packet-Switched network is connectivity to an IP network from the terminal to the GGSN node, via a bearer referred to as the PDP context. Its characteristics are different depending on what kind of service/information is to be transported. In case of WCDMA Radio Access Network (RAN), the PDP context in turn uses a Radio Access Bearer (RAB) service, with matching characteristics. The RAB in turn consists of a Radio Bearer between the terminal and the Radio Network Controller (RNC), and an lu bearer between the RNC and the core network.
The PDP context/RAB carries user data between the mobile terminal and the GGSN, which is acting as the access router to the IP network, e.g. Internet.
The PDP context/RAB is characterized by certain Quality of Service (QoS) parameters, such as bit rate and delay, service availability, maximum Bit Error Rate (BER), Guaranteed Bit Rate (GBR) and other measurements to ensure quality communications service. The terminal will request a PDP context from the Core Network, matching the needs of the application initiated by the user. The core network will select a RAB with appropriate QoS based on the PDP context request from the mobile terminal, and ask the RNC to provide such a RAB.
The QoS model of the wireless (cellular) network is currently discussed in the Third Generation Partnership Project (3GPP), which is a collaboration agreement that brings together a number of telecommunications standards bodies. 3GPP has defined four different quality classes of PDP context/Radio Access Bearers, with their characteristics:                Conversational (used for e.g. voice telephony), providing low delay and guaranteed bitrate;        Streaming (used for e.g. watching a video clip), providing moderate delay and guaranteed bitrate;        Interactive (used for e.g. web surfing), providing moderate load-dependent delay without guarantees on throughput/bitrate; and        Background (used for e.g. file transfer), which is the same as Interactive but with a lower priority.        
Both the Conversational and Streaming PDP contexts/RABs require a certain reservation of resources in the network, and are primarily meant for real-time services. They differ mainly in that the Streaming PDP contexts/RAB tolerates a higher delay, appropriate for one-way real-time services. The Interactive and Background PDP contexts/RABs are so called “best effort”, i.e. no resources are reserved and the throughput depends on the load in the cell. The only difference is that the Interactive PDP context/RAB provides a priority mechanism.
The QoS of the Cellular Network discussion in 3GPP is connection-oriented. It is based on establishing bearers with certain QoS classes. For the QoS class Interactive (and Background), the system does not reserve radio resources for the full lifetime of the connection (bearer). Resources need only be allocated when packets need to be transmitted. Therefore, no admission control is needed in relation to the setting up of the bearer.
QoS classes “Streaming” and “Conversational” provide a guaranteed bitrate, i.e. the system reserves bandwidth at the set up of the bearer. This implies the use of an admission control mechanism at bearer set up, whereby the system rejects a new bearer if it cannot guarantee the bitrate of the new bearer and the already admitted ones. A server system will deliver a datastream of e.g. audio to a client. The client receives the data stream and (after a short buffering delay) decodes the data and plays it to a user. Each bearer is identified as a Packet Data Protocol (PDP) context between the terminal and the Core Network, and as a Radio access bearer through the Radio Access Network (one-to-one mappings).
It is widely assumed that applications requiring strict QoS in terms of throughput and/or delay characteristics need to be mapped to a streaming/conversational bearer with guaranteed bit rate.
A user priority level may be assigned to users or devices within a communication network and is used to coordinate access privileges based on network activity or other factors. Priority handling can be achieved with an Interactive bearer, which is associated with a Traffic Handling Priority. In the state of the art, the subscription level, such as “Gold”, “Silver” or “Bronze”, is normally used to determine the priority level of a single Interactive bearer for the user.
If it is desired to use an Interactive bearer with a certain priority level for a specific service/application, the current art solution is that the terminal requests this bearer at service start time, and associates it with the flow of the particular service.
Within the radio access network, there are possibilities for providing priority scheduling between flows of different users, e.g. by intelligent channel assignments (packet services mapped to DCH) or priority scheduling in the base station (HSDPA).
At the cellular radio interface, there is a fundamental distinction between two cases of resource assignment:                Dedicated resource assignment. A radio resource (characterised e.g. by frequency, code, power) is assigned from the network to a terminal connection until explicitly released by the network.        Shared resource assignment. A radio resource is shared between many terminal connections, and is in a specific (short) time period temporarily assigned to a specific terminal connection. In the downlink direction, the network can typically make scheduling decisions based on availability of packets in buffers. In the uplink direction, there is a need for a protocol to resolve the situation when multiple terminals contend for the channel. Still, the final decision is in the network.        
In a WCDMA RAN system, there are different channel types. For dedicated resource assignment, there is one channel type being DCH (Dedicated Channel): used in both link directions. The channel can be configured with different rates (e.g. 64, 128, 384 kbps). Once configured for a certain rate, resources for that rate are reserved (even if not used), until the channel is released or reconfigured.
There also exist a number of channel types using shared resource assignment, as follows:                Forward Access Channel (FACH): Downlink direction. Typically low bit rate. Scheduling done by the RNC.        Random Access Channel (RACH): Uplink direction. Typically used only to transfer minor packets, such as signalling.        Downlink Shared Channel (DSCH): Downlink. Specified, but not used in networks. Scheduling done by the RNC.        High Speed Downlink Shared Channel (HS-DSCH), also referred to as High-Speed Downlink Packet Access (HSDPA): Downlink direction. Scheduling done by the Node B (base station). Very high bit rates supported. Also mechanisms to handle flows of different priority levels. Added to specifications in 3GPP release 5.        Enhanced Dedicated Channel (E-DCH), also referred to as Enhanced Uplink: Uplink channel being specified by 3GPP for release 6. Although using a dedicated code-channel, the network has control of the power/interference resource. This is done by the Node B (base station), which can limit the rates of different terminals, as well as schedule which terminals that are allowed to transmit at all.        
Important to note is that WCDMA includes the possibility for packet-switched bearers to switch between using the different channel types. For instance, a terminal with a packet-switched bearer (“Interactive” class) may use RACH/FACH when no data is being transmitted. When data arrives, the connection is switched to a DCH with a certain rate. If capacity exists, and the amount of data is high, the rate of the DCH may be switched up. For GSM RAN, the packet-switched services always use a PDPCH, which uses shared resource assignment. The scheduling is controlled by the BSC. Different priority levels can be used in the scheduling decisions.
A mechanism for providing Connectionless packet-by-packet priority handling on the Internet is for example provided by IETF (Internet Engineering Task Force) by means of Differentiated Services (Diffserv). Diffserv is a protocol that identifies different types of data with data transmission requirement flags (e.g. priority) so that the routing network has the capability to treat the transmission of different types of data (such as real-time voice data) differently. The goal of the evolving IETF Diffserv framework is to provide a means of offering a spectrum of services in the Internet without the need for per-flow state and signalling in every router. By aggregating a multitude of QoS-enabled flows into a small number of aggregates that are given a small number of differentiated treatments within the network, Diffserv eliminates the need to recognize and store information about each individual flow in core routers. This basic trick to scalability succeeds by combining a small number of simple packet treatments with a larger number of per-flow policing policies to provide a broad and flexible range of services. Each Diffserv flow is policed and marked at the first trusted downstream router according to a contracted service profile. When viewed from the perspective of a network administrator, the first trusted downstream router is a “leaf router” at the periphery of the trusted network. Downstream from the nearest leaf router, a Diffserv flow is mingled with similar Diffserv traffic into an aggregate. All subsequent forwarding and policing is performed on aggregates.
FIG. 2 shows an example of the mapping of application flows on bearers and down to channel types is done in a state of the art solution for WCDMA. Mapping from application to bearer type is done by the terminal, while mapping from bearer type to radio channel type is done by the RAN. Typically, any application with specific QoS requirements, such as Voice-over-IP (VoIP), streaming or other multimedia services, are mapped to a Conversational or Streaming bearer, with service specific attributes, including a guaranteed bit rate. The lower layer parameters for each such service-specific bearer needs also to be defined for interoperability reasons. The generic Interactive bearer is only used for web and other traffic with no strict QoS requirements.
The above-described current solutions have disadvantages, when using guaranteed bit rate bearers (streaming/conversational) to achieve a certain quality.
Firstly, these current methods and systems are too complex. For example because:                there is a need to perform signalling to set up a service-specific bearer at the start of the application session or flow;        each service needs to define a specific bearer with specific QoS parameters. All these bearers need to be implemented and tested for interoperability in different parts of the system. This increases the time to market for new applications.        a connectionless flow of priority marked packets, such as Diffserv IP packets, does not fit with the connection oriented bearer concept of the 3GPP QoS. There needs to be a signalling event to establish the priority Interactive bearer. It is unsuitable to establish and release such a bearer for every packet that arrives, according to the priority of each individual packet.        
Secondly the current methods and systems are not flexible enough. For example because an operator, charging not for the access but for a certain premium services, wants to fully control the QoS used for this service delivery, and not rely on the terminals mapping from service to bearer.
Thirdly, because in the current methods and systems there is a need to perform signalling at the start of the flow, a delay is encountered.